topological sort

class Node:
    def __init__(self, name):
        self.name = name
        self.nb = []
        self.visited = False

    def __str__(self):
        return self.name


class Graph:
    def __init__(self):
        self.nodes = []
        self.sorted = []

    def topological_sort(self):
        self.sorted.clear()
        for n in self.nodes:
            self.__visit(n)

    def __visit(self, node):
        if node.visited: return
        node.visited = True
        for n in node.nb:
            self.__visit(n)
        self.sorted.append(node)


a = Node('A')
b = Node('B')
c = Node('C')
d = Node('D')
e = Node('E')
f = Node('F')
g = Node('G')
h = Node('H')
i = Node('I')
j = Node('J')

a.nb[:] = [b, f]
b.nb[:] = [h]
d.nb[:] = [c, e, i]
e.nb[:] = [i]
g.nb[:] = [a, b, c]
i.nb[:] = [c]
j.nb[:] = [e]

G = Graph()
G.nodes[:] = [a, b, c, d, e, f, g, h, i, j]
G.topological_sort()

print([str(n) for n in reversed(G.sorted)])